Biology 3300- Trees

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Department
Biology
Course
BIOL 3300
Professor
Theresa Burg
Semester
Spring

Description
Biology 3300 th Feb.26 , 2014 Phylogenetic Trees Definition: the evolutionary relationships among organisms; the patterns of lineage branching produced by the true evolutionary history of the organisms being considered Anatomy of a Tree - Nodes  most recent common ancestor; when speciation occurs; new species are being created - Transitions  introduces a new characteristic Each phylogeny is based on the characters and the number of taxa used - Each will be different due to the data that is used Species existed along branches, not just at the tips Derived trait is found in some of the lineages of taxa, but not in others. Traits can be derived or ancestral. Closely related species have similar traits. Trees are not ladders Order does not imply “advancement” - Something on the left is not more simple than something on the right - Order has nothing to do with how simple or complex organisms are There is more than one way to draw a tree - The two trees are the same the node was just turned - Both show the mammals together - Go down the branches to see where they show common ancestors Different Ways to Draw Trees - Networks are more common in many individuals of different populations o Essentially B gave rise to both A and C - Bifurcating tree o Forces everything into pairs o Still shows that B is a common ancestor of A and C The tree that you get is dependent on the data and the taxa you use The number of taxa you use can result in a number of possible trees #OTU # unrooted trees 4 15 8 >10,000 10 2 million 100 2x10 182 OTU = operational taxa unit Unrooted trees  do not know who the ancestor is Homologous trait: want to use traits derived from a common ancestor Synapomorphy: essentially a shared, derived trait - Originate before a node - Used to identify related groups - Nested - Needed to build tree Steps: - Select characters and outgroup - Construct matrix - Build tree What is the direction of change? - Ancestral or derived? - How do we know what character state was in the common ancestor? o Fossil record  can be good or bad for different species (bad for
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